Method and apparatus for making steel

ABSTRACT

Method of converting a single-basin open-hearth furnace into a dual-basin furnace for preheating the steel in one basin while working molten metal in the other basin.

United States Patent .9

William A. Morton;

Alfred S. Sobek, both of Pittsburg, Pa. 844,220 1 Mar. 13, 1969 Aug. 31,1971 Sunbeam Corporation Division of Ser. No. 632,854, Feb. 17, 1967,Pat. No. 3,495,974

Inventors Appl. No. Filed Patented Assignee METHOD AND APPARATUS FORMAKING STEEL 4 Claims, 13 Drawing Figs.

u.s.c| 266/39, 29/401, 75/45, 266/34 mci C2lc7/00 [501 Field of Search29/401;

I [56] References Cited UNlTED STATES PATENTS 2,063,402 12/1936 Rossman75/43 3,060,014 10/1962 Aihara 75/43 3,219,439 11/1965 Longenecker 75/603,169,159 2/1965 Jackson 266/34 Primary Examiner-Gerald A. DostAttorney,sHoopes, Leonard & Buell and Buell, Blenko and ZiesenheimABSTRACT: Method of converting a single-basin openhearth furnace into adual-basin furnace for preheating the steel in one basin while workingmolten metal in the other basin.

PAIENTEDAUBM I97! wit m W w szz. WMS. NZ 3%. m w} M A rrom/svs PATENTEDAUBB I ISYI SHEET '5 OF 9 Fig .50.

CONVENTIONAL PROCESS- OXYGEN FIRED H T R A E H N M m D H R 3 A D N E A TS J. N N s l 0mm M MZT E a L m H C R P I Aww B C 2? 4.5 HRS.

PRODUCTION 350 TONS PRODUCTION PER MIN. L3 TONS PROCESS OF PRESENTINVENTION Fig .5b.

m 5 TAP m L W T W A E A T 0 E R E L HIT P H M 8 M IRON P SCRAP m N TCLEAN T m E T A o M R H E TAP 5 O P H T w 6E M w 9P SCRAP P B W CLEAN NRON WW 6 I UU TAP I M T W DD. W E E A 9 COT w HIV m E RRA B F- H PPR RONP SCRAP T CLEAN N E T A 6 8 I 3 w M .W. TAP H E w R w SCRAP P B T. IwCLEAN 0 RON m m TAP w T T W A E A 9 O W E M E 2 H H B m m IRON P SCRAPCLEAN M E T T 6 w R M U TAP I P H u W l R ZSCRAP P B WCLEAN RON Fig .5c.

HEAT CONTENT OF MATERIALS PER TON OF CHARGE BASIC OXYGEN CONVERTER 70%LIQUID PIG IRON 532,000 BTU SCRAP COLD (ROOM TEMP.) 5 320 BTU 537, 320BTU AVG. TEMR IGBO'F.

TOTAL CONVENTIONAL OPEN HEARTH 60% LIQUID PIG IRON 460,000 BTU 40% SCRAPCOLD (ROOM TEMP.) 7, 200 BTU 467, 200 BTU AVG. TEMR IOE TOTAL 388,9OOBTUAVG. Tenn-mow.

PROCESS OF PRESENT INVENTION uoum PIG IRON 300,000 BTU PREHEATED (momROOM TEMP.)

50% LIQUID PIGIRON 380,000 BTU P A R C S 0 5 E MT EM H0 0 HR WM L 0 C Nl T N E V N o C TOTAL 50% SCRAP 240,000 BTU Alfred S. Sobok PATENTEDAUG31 19m SHEET 8 UF 9 METHOD AND APPARATUS FOR MAKING STEEL Thisapplication is a division of application Ser. No. 632,854, filed Feb.17, 1967, and now U.S. Pat. No. 3,495,974 which is a division ofapplication Ser. No. 328,067, filed Dec. 4, 1963, now U.S. Pat. No.3,342,470, which is in part a continuation of application Ser. No.246,492, filed Dec. 21, 1962, and now abandoned.

The present invention relates to a new and improved method and apparatusfor making steel, and more particularly to a new and improved method andapparatus for producing high quality steel from a combination of moltenpig iron and cold scrap metal.

In the United States, at the present time, about 80 percent of the totalsteel production is produced in open-hearth furnaces, either basic oracid with approximately percent being produced by the basic oxygenprocess and the remaining percentage being attributed to electricfurnace and other types ofproduction.

Open-hearth furnaces are fired with fuel derived from an external sourcesuch as natural gas, manufactured gas, gas derived as a byproduct inother steelmaking operations, and the like. The flame and heatedcombustion are directed onto and across the metal in the hearth tooxidize impurities in the metal. The process of heat transfer is notefficient, however, and large amounts of fuel are required in the openhearth to refine a heat. For example, 3%million B.t.u.s may be requiredfor each ton of steel in the heat, although nearly double that amounthas been observed in commercial practice. The openhearth process is arelatively slow one due to the slow rate of heat transfer and refining.The time to refine a typical heat may be, for example, about 10 hours.Thus in a furnace of 200ton capacity, the production rate is on theorder of tons per hour. The cost of open-hearth furnaces is high. Atypical installation may have a cost of 60 million dollars for aninstalled capacity of 2 million tons of steel per year. In consequenceof the foregoing, the cost of refining steel in an open'hearth isrelatively high often as much as $8.00 per ton, or more.

The open-hearth process can, because the furnace is externally fired, beused to refine charges of pig iron and scrap in any proportions to goodquality steel. It can, for example, satisfactorily refine a heat inwhich the charge is entirely cold scrap. Since the firing rate canreadily be controlled, it can also handle a charge which is entirely ofhot metal, such as in the duplex process.

In recent years commercial grades of oxygen have become available incommercial quantities and at prices low enough to make their useeconomically feasible. Many conventional open-hearth furnaces have beenfired with oxygen in place of atmospheric air. That practice hasincreased the firing rate, increased the operating temperatures andspeeded up the refining process in some degree. A reduction in refiningtime of about 50 percent may be considered as typical. Production costshave, in consequence, also been lowered somewhat.

The basic oxygen process has come into commercial use since thedevelopment of commercially feasible oxygenproducing plants. In contrastto the open-hearth process, the basic oxygen process is carried outsolely by the heat of exothermic reactions between impurities in thecharge-notably carbon, sulfur, and silicon-and a jet of oxygen directedinto the vessel. The reaction taken place in intimate contact with thecharge, and the heat of the reaction is transferred directly to thecharge instead of large quantities of heat passing up the stack as in anopen-hearth plant. A typical installation having a capacity of about 2million tons per year costs less than half as much as an open-hearthinstallation of the same capacitygenerally about one-third as much.Moreover, a basic oxygen converter having a vessel capacity of 200 tonswill produce about 10 times as much as a standard open-hearth furnace ofthe same size because of the shorter production cycle. Even when an openhearth is fired with oxygen, the production rate of the basic oxygenprocess is greater than the open-hearth process in a furnace of the samesize. Since the basic oxygen I a minor constituent. The charge must beabout 70 percent or more hot metal, since if less is charged, the chargewill not have enough heat to carry the refining process through tocompletion. If the charge were entirely cold scrap, the reaction would,of course, never begin. Accordingly, the basic oxygen process is onewhich is heavily dependent upon a supply of hot metal. It is unable toadvantageously use large quantities of scrap in those countries andunder those economic conditions in which scrap is plentiful and low inprice.

In the operation of an open-hearth furnace, the charges of cold scrapand that of molten pig iron are added progressively in the ordermentioned during the heat as the molting of the metal on the hearthproceeds. Refining is accomplished with heat from the burning of fuel inan atmosphere with considerable excess air. Ordinarily 50 percent ormore excess air is admitted to the furnace. The hearth is constructed toform a pool of metal of shallow depth in order to provide a largesurface to absorb heat and oxygen from the burning fuel and gasespassed" over this surface. In a conventional open hearth, a number ofcharging doors are provided along the sides for the addition of thecharge. The charging of cold scrap is a slow operation because of thelength of hearth, the number and size of doors through which thematerials have been charged and the limitations of existing equipment.Throughout the charging time the doors are open for extended periods andlarge quantities of cold air infiltrate into the furnace, cooling it asignificant amount. The heat lost in that fashion must, of course, berecovered by further firing, causing an expenditure of both fuel andtime.

In a basic oxygen converter the problem of charging time and heat lossis less acute, since the vessel is much deeper and can be tilted toreceive the charge which is discharged quickly by gravity through thenarrow mouth of the converter. The charging time of the basic oxygenconverter is a matter of 3 to 5 minutes compared with an hour to two remore hours for the multiple door open hearth.

We provide steel-refining apparatus comprising a single furnace having apair of adjacent open receptacles in juxtaposition. We preferablyprovide two abutting hearths placed within a single unobstructed anduncompartmented furnace. We preferably provide access door meansextending for a substantial length of each hearth and charging machineswhose capacity is such that the hearth can be substantially completelycharged within relatively short time. We further prefer to provide meansfor refining metal in one of the receptacles and passing the heatresulting therefrom across a relatively cold unrefined charge containedin the other receptacle. We further provide means to direct streams ofoxygen against the charges in the hearths and preferably supply a fuelwith the oxygen. We prefer to provide jetting means for use upon thecharge being refined and separate jetting means for use upon the as yetunrefined charge.

We preferably provide high-capacity scrap-charging means effective tocharge substantially a complete charge of scrap within relatively shorttime. In our preferred embodiment, we provide tilting bin means adjacentthe access door means for rapid discharge of scrap into the furnace upontilting of the bin means. We preferably provide chute means wherebyscrap is directed into the furnace through the access door means withoutspilling.

The invention overcomes many of the disadvantages and limitations bothof the open-hearth and basic oxygen processes, and provides aflexibility and economy that cannot otherwise be achieved. The processof the invention enables steel to be refined from a charge of molten pigiron and cold metal in any desired proportions. In the preferredpractice, substantial quantities of each are employed. The molten chargeof pig iron and scrap is blown with oxygen to refine the metal byexothermic reaction to the characteristics of steel desired. Thereactions which take place are the oxidation of various impurities suchas carbon, sulfur, and silicon with the oxygen at elevated temperatures.The oxygen is a commercial grade now widely used in various industrialprocesses and being about 98-99 percent pure. Nitrogen, whichconstitutes about 80 percent of atmospheric air, has been substantiallyeliminated. Fuel may be supplied with oxygen from an external sourcewhere it is desired to supplement the heat developed by the reaction ofoxygen with various impurities contained within the charge. The hightemperature gases emitted from the molten charge as it is blown in onereceptacle of a furnace are directed to and across an adjacentreceptacle of the furnace containing a fresh charge of cold metal andare passed in intimate contact with the fresh charge, preheating it to ahigh temperature. A further charge, including the desired amount ofmolten pig iron, is then introduced into the receptacle with thepreheated constituents. This charge is then blown with oxygen in thesame manner as the charge in the first receptacle. The hot gases emittedtherefrom are utilized to preheat a new charge of cold metal which hasbeen placed in the other receptacle after the original charge wasremoved. Thus, the two receptacles are alternately used as thepreheating receptacle and as the refining receptacle.

Additionally, since the hot gases emitted from the blowing operationcontain considerable carbon monoxide, oxygen is mixed with these gasesto convert the carbon monoxide to carbon dioxide. That reaction isexothermic and develops substantial additional heat for preheating thecold charge. Thus the new and improved apparatus of the presentinvention includes a furnace having two adjacent receptacles, one forcontaining a charge of metal as it is blown, and one for containing afresh charge of cold metal for preheating. Means are provided in thefurnace for introducing and removing the charges from the receptacles,and oxygen lance means are provided for alternately blowing the chargesin the receptacles in order to refine them into steel. Additional air oroxygen lance means are provided between and above the adjacentreceptacles for alternately directing the hot gases emitted from thecharge being blown into intimate contact with the cold charge in theadjacent receptacle in order to preheat it to a high temperature and toprovide additional heat by oxidizing the carbon monoxide in the emittedhot gases into carbon dioxide. The additional lance positioned over thescrap charge will be positioned at a substantial level above the scrapto deliver oxygen to the carbon monoxide in the waste gases and directthe resultant products of combustion downwardly into the center of thescrap receptacle. There is also provided new and improved apparatus forrapidly charging the furnace with scrap or other cold metal so that thecharge enters the furnace in such a manner that damage to the refractorylinings of the receptacles is held to a minimum.

In the foregoing manner steel may be produced from scrap and pig iron invarious percentages not heretofore obtainable without a supply of fuelfrom an external source. The invention may be carried out in a furnaceof well-known design such as the open-hearth type. Existing open-hearthinstallations may be reconstructed to practice the invention atsubstantial cost savings. The heat from the exothermic reactions in onehearth of the furnace is used to preheat the charge in the other hearthmaking it possible to utilize higher percentages of scrap thanheretofore without use of external fuels. Even where use of externalfuels is desired or necessary, the amount required is reduced. Thepreheating reduces the time required to refine the charge to a finishedstate and makes possible cheaper and faster production from theequipment. The invention permits quick easy charging of metal intohearths of such depth that the charging process is a facile one whichmay be carried out quickly and expeditiously in a small fraction of thetime previously considered necessary in furnaces of the type provided.

. partly in phantom, of one embodiment of a furnace and attendantapparatus for producing steel constructed in accordance with thefeatures of the present invention shown with apparatus functioning withthe right-hand receptacle being used to refine steel while the left-handreceptacle is used to preheat scrap; I

FIG. 2 is an enlarged top plan view, partly in section, of a portion ofFIG. 1 showing the new and improved furnace embodying certain featuresof the present invention;

FIG. 3 is a side elevational view of the furnace of FIG. 2, partly insection, taken substantially along the line 3-3 of FIG. 2, and assumingthat FIG. 2 shows the complete structure and showing the location ofcertain parts in phantom;

FIG. 4 is a sectional view taken substantially on line 4-4 of FIG. 3assuming that FIG. 3 shows the complete structure;

FIGS. 5a, 5b and 5c are somewhat graphical representations to aid inunderstanding the present invention;

FIG. 6 is an enlarged view of a portion of FIG. 1 illustrating thecharging apparatus of the present invention;

FIG. 7 is a side elevational view of the apparatus of FIG. 6 takensubstantially along line 77 of FIG. 6;

FIG. 8 is an end elevational view of the apparatus of FIG. 6 takensubstantially along line 88 of FIG. 6;

FIG. 9 is a top plan view, partly in section, similar to FIG. 1schematically illustrating the furnace of the present inventionutilizing another embodiment of a charging apparatus constructed inaccordance with the present invention;

FIG. 10 is a sectional view of the charging apparatus takensubstantially along line 10--10 of FIG. 9 assuming that FIG. 9 shows thecomplete structure; and

FIG. 11 is a side sectional view taken along line 11-11 of FIG. 9.

Referring now to the drawings, there is illustrated in FIG. 1, apparatusfor the production of steel constructed in accordance with the featuresof the present invention which include a furnace l2 and charging system13. The latter is movably mounted on rails 14 which extend for somedistance along the furnace 12 in order that the charging system can beloaded with the proper amounts of the various ingredients which arestockpiled elsewhere and also so that the charging system can be used tocharge each of the portions of the dual open-hearth furnace of thefurnace of the present invention. The ends of the furnace 12 areconnected to a suitable stack 15 as by passageway sections 10a and 10b,shown in phantom, which conventionally might be located underground.

The furnace 12 is illustrated in detail in FIGS. 2, 3 and 4 of thedrawings and includes a supporting section which might be designatedbroadly as a hearth having a pair of adjacent charge-receivingreceptacles 18 and 20. Receptacles 18 and 20 may themselves properly bereferred to as hearths in which separate refining actions are carriedout. The hearth and receptacles therein are built of several layers ofrefractory material 22 in the usual manner and the structure is carriedby a steel frame floor 24 supported in the center by posts 20 and at theends by a plurality of steel columns 28.

In order to provide for the proper. depth of the receptacles 18 and 20,the furnace is provided with structural sidewalls 30 and 32 which runthe length of the furnace on both sides of the receptacles. Thesidewalls 30 and 32 terminate along a horizontal plane designated as 34(FIGS. 3 and 4) which for a particular embodiment was approximately 3feet above the level of the charging floor designated as 36 adjacent thecharging side of the furnace. Internal and structures 38 (FIG. 3) and acentral structure 40 supported from the frame 24 are are also providedto give support for the walls of the receptacles 18 and 20.

The receptacles 18 and 20 are somewhat deeper than is the case with thenormal open-hearth furnace since oxygen is used for blowing the chargestherein and a large' surface area of the molten charge is not required.In a specific embodiment, the maximum depth of these receptacles fromthe surface of the molten charge was in excess of 4 l feet as comparedwith a 30- inch depth customarily used in open-hearth installations.This added depth increases the capacity of the furnace 12 to holdapproximately the same volume of charge as a converted open-hearthinstallation having a larger area but shallow depth.

At both ends of the furnace 12 there are provided the chambers 42 and 44for directing the flow of gases over the receptacles in the desireddirection. This accomplished by suitable damper means 45 (FIG. 1)controlling which passageway 16a are in communication with the fluesystem 16a and 16b of the furnace 12 through outlets 50a and 52a in thesidewalls of the pits. Slag or other material flowing over the end walls46 and 48 will drop directly into the slag pits 50 and 52 while gasesflowing through the. chambers 42 and 44 will pass through the pits andoutlets 50a and 52 a therein into or from the flue system of the furnaceas the case may be.

The chambers 42 and 44 are provided with refractory lined end walls 42aand 44a, sidewalls 42b and 44b ceiling walls 42c and 44c extend inwardlypast the end walls 46 and 48 of the hearth and conform generally to theshape of the ceiling walls over the hearth itself. The sidewalls 42b and44b intersect end walls 54 and 56 of the furnace (FIG. 2) which areprovided with openings 54a and 56a, respectively, in order that thegases may pass to the chambers 42 and 44 after passing over thereceptacles 18 or 20, respectively.

A furnace roof confines the heat from the furnace and provides anenclosure channeling the gases evolved by the reactions in one hearthacross the cold charge in the other hearth. The roof comprises aplurality of removable cover members 53 and 60 which are positionedadjacent each other to overlie the receptacles 18 and 20, respectively.The cover members 58 and 60 which are positioned adjacent each other tooverlie the receptacles l8 and 20, respectively. The cover members 58and 60 are identical and are each provided with an arched ceiling 62(FIG. 4) constructed of refractory material supported by a plurality ofsteel frames 64. The cover members are provided with steel bar flanges66 attached thereto which rest and are attached to the top surfaces ofthe sidewall structures and 32 when the covers are in place. Each of theframes 64 is provided with a vertical slot 68 through which the lift barof a crane or other device can be inserted in order that the covermember can be readily lifted bodily from the'furnace or replacedthereon.

So that each receptacle 18 and 20 may be charged, each cover member 58and 60 is provided with a large opening 70 through which bulky scrapmetal can be supplied to the receptacles 18 or 20 and a smaller opening72 for charging the receptacles with molten metal. These openings, shownin phantom in FIG. 3, are positioned to lie adjacent the charging floor36 in order that charging materials can be fed through openings 70 fromthe charging system described in detail hereinafter, and molten metalfrom metal-containing ladles can be supplied through openings 72.

In order to maintain the high temperatures of the furnace and to reduceheat loss, the openings 70 are provided with upwardly slidable chargingdoors 74, which may be water cooled, and the openings 72 are providedwith similar smaller doors 76 (FIG. 3). These doors, which may be ofconventional design, are supported for sliding movement by doorframestructures (not shown) which, if desired, may also be water cooled. Thefurnace 12 is provided with channels 82 (FIGS. 1, 2, and 4), one foreach opening 70, which interconnect the openings 70 and their respectivereceptacles l8 and 20. Each of the receptacles 18 and 20 isprovided'with a molten-metalcharging chute 84 which communicates withits respective opening 72 in order that the molten metal charge which issupplie'd through the charging door 76 will flow into the desiredreceptacle 18 or 20 as the case may be. These charging chutes 84 causethe molten metal to enter the receptacles 18 or 20 in a tangentialmanner.

There is provided exteriorly of the wall 30 of the hearth 16 adjacenteach opening 70, a front flush chute 86 which receives the molten slagwhich must be removed from the furnace to carry away fluxe d impuritiesbefore the molten heat is tapped from the hearth.

So that finished steel can be removed from the receptacles 18 and 20 inthe usual manner, each of the receptacles is provided with centrallylocated bottomtapholes 88 which communicate with disehargechutes 90through tapping passages 92. The discharge chutes or spouts lead toaconventional pouring ladle 93.

In accordance with the present invention, and in order to provide forthe refinement of the charge in the receptacles l8 and 20, each covermember 58 and is provided with a central aperture 94 in the roof thereofthrough which an oxygenfuel lance 96 can be extended to flow the chargein the receptacle. The oxygen-fuel lance is supported from the lancehoist 78 and is alternately lifted and lowered through the cover member.The two lances provided over the adjacent receptacles are usedalternately to blow the charges in the receptacles l8 and 20 duringoperation of the furnace. Each lance has an individual hoist such asthat shown in FIG. 4. A lifting winch 78 is mounted on rails 80 and isoperable to raise and lower lance 96 which is hung from the end of acable wound on the drum of the winch. Each lance 96 may optionally besupplied only with oxygen or with a fuel-oxygen mixture as operatingconditions require. Both lances may be employed simultaneously -one toblow the charge being refined, and the other to preheat the charge inthe other hearth or receptacle, supplementing the heat generated by therefining process in the first hearth or receptacle.

There is also provided in each cover member a plurality of angularlydisposed openings 99 through which extend a plurality of removablemounted oxygen or air lances 100 (FIGS. 2 and 3). Because of theirangularly disposed arrangement, the air supplied thereto can be directedin either direction depending on the particular receptacle 18 or 20where preheating is taking place, The auxiliary lances 100 are at anangle to direct the airblast toward the center of the receptacle 18 or20 in which a charge is being preheated. The air lances 100, one beingshown in dotted lines in FIG. 3 (associated with cover member 58), areused when the receptacle 18 is used for preheating. When the receptacle20 is being used for preheating, the lances associated with cover member60 are employed.

In the operation of the furnace 12, a molten charge generally comprisinga mixture of scrap metal and pig iron is disposed in one of thereceptacles such as 18 and this charge is ready for refinement to steel.At the same time a charge of cold scrap is placed in the adjacentreceptacle 20. The oxygen lance 96 is then lowered into place over thereceptacle 18 and the molten charge therein is blown with this oxygenlance resulting in the burning out of the impurities. Due to thechemical reactions involved, large quantities of heat are produced andthere is frequently no necessity as in the conventional open-hearthfurnace to burn fuel for producing heat. The blasts of air or oxygenfrom auxiliary lances combine with the gases emitted from the charge inreceptacle 18 being blown. Since those emitted gases contain largeamounts of carbon monoxide, oxygen from the air lances 100 and theadjacent lance 96 intermixing therewith the carbon monoxide causes muchof the latter to be further oxidized to carbon dioxide thus producingadditional heat by this exothermic action. These hot gases are directedby the superatmosphere metal in receptacle 20 causing it to be preheatedup to temperatures-of l,500 F. or higher, depending upon the percentageof scrap in the steel mix and the physical form of the scrap which maylimit the effectiveness of the heating. It should be noted that thedirection of the lances burning the carbon monoxide in such that themixture of the resultant gases and those emitted from the receptacle 19is directed downwardly toward the center of receptacle 20 to provideintimate contact therewith to preheat the charge of scrap metal placedtherein. By the time the blowing process is completed in the receptacle18, the cold scrap in the receptacle 20 has been heated to about 1,500F. by extraction of heat from the gases which would otherwise pass onout through the chamber 44 and pit 52 to the flue system comprisingpassageway 16b and stack 15. The taphole 88 in the receptacle 18 is thenopened and the refined steel therein passes through the passage 92 andspout to the pouring ladle 93.

The oxygen lance 96 is then retracted through the cover member 58 duringthe subsequent charging operation. The oxygen lance 96 associated withcover member 68 is lowered for use therein. A molten pig iron charge isthen introduced into the receptacle 20 containing the preheated scrapthrough opening 72 in the cover member 60 normally closed by chargingdoor 76. This pig iron flows through the charging chute 84 intoreceptacle 20 mixing with the preheated scrap contained therein.

While this is going one, receptacle 18 is cleaned and the taphole 88therein is plugged in preparation for receiving a charge of cold scrapiron which is placed therein from the charging system 13 through theopening 70 in the cover member 58 controlled by door 72. The moltencharge in the receptacle 20 is then blown with oxygen from theassociated lance 96 in the same manner as described above in connectionwith the charge in receptacle 18. Cases emitted from this blowing arefurther oxidized by the air from the auxiliary lances 100 and themixture is directed by those lances into intimate contact with the coldscrap charge in receptacle 18 causing it to be preheated as beforedescribed. During this operation, the flow through the furnace isreversed with the gases leaving through the chamber 42 and pit 50 intothe flue system comprising passageway 16a and stack 15. Thus, the dualreceptacles are alternately used to refine the molten charge to steeland to preheat the cold scrap.

Referring now to the graphical illustrations of FIGS. a, 5b and 50, FIG.5a illustrates the operating cycle of a typical standard open-hearthfurnace having a hearth capacity of 350 tons and fired with oxygen. Ascrap charge of 140 tons comprising choice heavy materials may be addedat the rate of approximately 2 3/ tons per minute. The pig iron chargeof 210 tons is added at the rate of 7 tons per minute. This chargecomprising 40 percent scrap and 60 percent molten pig iron is heated inn extremely well-organized operation for about 3 hours giving a totalproduction of 300 tons or approximately 1 3/10 tons per minute.

FIG. Sb illustrates the process carried out in the furnace of thepresent invention of approximately the same physical size havingreceptacles 18 and 20, each having a capacity of 160 tons. The timecycle in each receptacle takes 90 minutes with the first 2 minutesutilized for charging with cold scrap. The cold charge is then preheatedfor about 38 minutes while the charge in the other receptacle is beingblown. Next 80 tons of molten pig iron are introduced at the rate of 8tons per minute for 8 minutes. The charge of preheated scrap and moltenpig iron is then blown with oxygen for minutes and tapped after theblowing. Allowing 10 minutes for removal of the finished steel andanother 10 minutes for cleaning and plugging the tap in preparation forthe next charge. The cycles in the receptacles are staggered timewise inrespect to one another so that the blowing operation in one takes placeduring the first portion of the scrap-charging cycle of the other, thusutilizing the heat developed during the blow for preheating the charge.Damper 45 is operated, of course, at the end of each cycle so that thehot gas evolved in the refining is forced to leave the furnace at themost remote of chambers 42 and 44.

Thus, it can be seen that than-c ient invention provides for aproduction rate of 960 tons during the same interval during which theconventional open hearth, fired with oxygen, produced only 350 tons or aratio of approximately 2 73/100 to one for the same size installation.If the same furnace were not oxygen fired, a time of 10 hours per cyclecould reasonably be expected. A ZOO-ton basic oxygen converter on theother hand will have about one cycle per hour.

FIG. 5c is a representation comparing heat content of materials per tonof charge in the various present-day process of refining steel and alsothe dual-receptacle furnace of the present invention. This comparisonshows the great advantage of the present invention over the old processin both temperatures attained and the percentage of the charge requiredto be liquid pig iron.

The use of removable covers 58 and 60 over the receptacles 18 and 20greatly reduces the shutdown time required for refractory repairs ascompared with the conventional openhearth furnace. In conventionalopen-hearth furnaces the top of the enclosure can only stand a limitednumber of heats before it is necessary to shut down the furnace torepair and rebuild the enclosure. This is not a limiting factor in thepresent invention, however, because of the removable cover members whichmight also be water cooled. Moreover, repairs on the cover members areeasier since the member is removed from the hearth for easy access and along waiting period for cooling before work is begun is not a limitingfactor since five or six cover members can be provided for eachinstallation with repaired ones always ready for use.

An important feature of the present invention resides in the fact thatexisting open-hearth installations can readily be converted to the dualreceptacle furnace of the present invention with a relatively lowinvestment. This eliminates the necessity of abandoning existingfacilities because high production and low operating costs can beobtained with the process and apparatus of the present invention. Theconversion consists primarily in changing the hearth to provide tworeceptacles 18 and 26) instead of one, and, of course, making thesereceptacles much deeper than the depth of the previous open-hearthreceptacles. These two receptacles of a specific comparable totalcapacity can be provided in the same of less space as far as surfacearea is concerned. Of course, the roof structure must be changed andfast charging means provided to achieve the results and possible by thismethod.

Moreover, since the basic oxygen converter is limited to a maximumcharge of 30 percent cold scrap, the process of the present inventionshows a decided advantage in being able to utilize up to approximately a50 percent charge of cold scrap by preheating it. Further the preheatingfeature of the present invention reduces the cost per ton of steel belowthat of steel produced either by the open-hearth or basic oxygen processby using an available fuel now being wasted by the steel industry.

From the above description, it is apparent that the charging system 13for the furnace 12 of the present invention must be capable of readilyalternately charging both receptacles l8 and 20 without delay. In FIGS.6, 7 and 8, one charging apparatus 13 of the present invention isillustrated in detail, which apparatus is at present considered thepreferred embodiment because it can readily be applied to existingopenhearth installations fitting within the existing structurescustomarily involved. This charging system is designed to beself-propelled along he rails 14 (FIG. 1) provided on the charging floor36 in order to receive boxes of scrap at a loading position of thedesired king which is stockpiled and charged into the removable boxeselsewhere.

The charging system includes an undercarriage 119 comprising a pair ofparallel side undercarriage members 120 and transverse undercarriagemembers 122. This undercarriage is supported on flanged wheels 124 whichroll along the rails 14 thereby moving the charging apparatus 13supported thereon. The wheels 124 are driven by suitable drive means(not shown) which are controlling from a control house 126 (FIG.

6) supported on the undercarriage 119 to move therewith. Theundercarriage 119 provides a framework for supporting a slidable mountedchute carriage 128 shown by solid lines in FIG. 7 in its chargingposition and by dotted lines in its retraction position. The chutecarriage is supported on lower rollers 130 and upper rollers 132, thelatter being mounted on structural members 134 (FIG. 8) running parallelwith the members 120.

For the purpose of charging the receptacles l8 and 20, there is provideda chute 136 having a gently sloping bottom 1360 (FIG. 7) and sidewalls136b (FIG. 8) joined thereto. The chute 136 is generally U shaped intransverse cross section as shown in FIG. 8 with the bottom 136a beingslightly concave and curving into rounded corners joining the sidewalls136b in order that scrap metal in the chute 136 will easily flowtherethrough with a relatively uniform flow without collecting the thecorners and without moving the batches. The sidewalls 136b in order thatscrap metal in the are flared widely at the top away from the chute exitas indicated at 136a in order to receive without spillage a charge ofscrap metal from either one of two elongated removable tiltablescrapboxes 138 and 140. The chute 136 is shown in the extended positionby solid lines (FIG. 7) and in the retracted position by dotted lines.

In accordance with the present invention, the scrapboxes 138 and 140 aresupported on a framework 142 carried by vertical lift hydraulic cornersupports 144 which in turn are supported from the undercarriage 119. Thehydraulic comer supports 144 permit the chute end of the scrapboxes 138ad 140'to have a variable height, thus permitting proper positioningand/or layering of the scrap as it is deposited in the reception 10 or20. As illustrated, the scrapboxes are generally U shaped in transversecross section and are convexed longitudinally as indicated at 145 (FIG.7) and are open at their forward ends so that scrap metal loaded thereinwill slide out into the chute 136 when the boxes are tilted. The angleof repose changes progressively as the boxes are tilted thereby causingthe scrap to flow in increments rather than on masse. The forward endsof the scrap boxes are pivotally mounted on an axle 150 or the like inorder that the rear of the boxes may be elevated by suitable means suchas the hydraulic lift means 151 illustrated, thereby to feed thematerial from the boxes 138 or 140 progressively into the chute at thedesired rate and, consequently, into the furnace at the desired rate. InFIG. 7, a tilted position of the scrapbox 140 is shown in dotted lines.Also FIG. 7 shows in solid and dotted lines the lowermost and uppermosthorizontal positions of the scrapbox 140 as controlled by hydraulicmeans 144.

In order to direct the scrap metal from either scrapbox 138 or 140 intothe chute 136, a feed hopper of guide chute 152 is provided at theforward end of the boxes. This hopper or guide chute is supported fromthe frame 142 and is provided with a free-moving swivel gate 154. Thisgate 154 automatically moves to open the scrap passageway independentlyof which scrapbox 138 or 140 is being emptied and it directs the flow ofscrap from the desired box into the the scrap chute 136. The hydrauliclifts 151 which selectively tilt the boxes 138 or 140 to the desiredtilt angle for providing the proper rate of flow of the scrap and byvirtue of the vertical lifi supports 144 the desired height of thedischarge end of the chute relative to receptacles 18 and is alsocontrolled.

In operation the charging apparatus 12 id movable along the rails 14 anddesired types and amounts from various supplies of scrap are loaded inthe boxes for making up each scrap metal charge for the furnace. Thesystem is then moved into position for charging the furnace as shown inFIG. 1 and the door 74 of the furnace adjacent either the receptacle 18or 20 is opened. The charge chute 130 is then extended through theopening 70 in the furnace and either of the scrapboxes 138 or 140 islifted allowing the scrap therein to slide out progressively through thehopper 152 into the chute 130 and then the furnace from a desired heightand at a desired rate.

By adjusting the charging apparatus 12 is movable the amount of tilt ofthe scrap boxes 138 or 140 as they are progressively lifted by thelifting means 151, the proper charging rate into the furnace can beeasily controlled. This flexibility of control is desirable since somecharges might not flow as easily as others and the rate of flow issomewhat dependent on the amount of head of scrap material left in thebox at any given instant and because of the shape 'of the floor of boxes138 and 140 it is necessary to increase the tilt angle as the scrapmoves out of the scrapbox. The rounded comers of the scrapboxes andcharging chute eliminate or reduce the tendency of the scrap to hang upand it should be noted that by providing a charging chute having verylittle elevation at its exit end, which is adjustable, and'varying theangle of tilt of the scrapboxes during charging, the ballistic problemof the cold scrap striking or gouging the walls of the receptacles 18 or20 is eliminated or greatly reduced. It should also be noted that thehorizontal section of the scrap chutes as it leaves the boxes must neverbe decreased or the scrap will jam. On the other hand, by causing thescrap to drop slightly to the chute, the cross section of the scrap isautomatically reduced as is the friction and the movement is thusaccelerated.

. In FIG. 9, 10 and 11 there is illustrated another embodiment of acharging apparatus readily useable with the furnace 12 of the presentinvention. This apparatus which is generally designated by the referencenumber 100 is adapted to move along the rails 14 on the charging floor36 for charging the dual open-hearth furnace 12. The corresponding partsof the furnace in FIGS. 9, 10 and 11 are designated by the samereference numerals'as in the preceding embodiments.

The charging apparatus is provided with an undercarriage 161' comprisingapparatus 160 is provided with an undercarriage 161 comprising a pair oflongitudinal under carriage side members 162 having rollers 164 thereonwhich roll along the rails 14. The side members 162 form a structuralpart of a support platform 166 on which the various parts of thecharging system are supported. For this purpose there are providedcornerposts 168 which extend upwardly from the platform to form asupporting structure for a scrap-supporting unit 170 including pluralityof compartments or bins 170c, 170b, 170c and 170d. As illustrated, thesescrap bins or compartments are supported as an integral unit. Thescrap-supporting unit 170 is rotatably supported relative to theplatform 166 in order that any selected bin 170a, 170b, 1700 and 170dcan be positioned adjacent the charging doors of the furnace 12. Thebins 170 are provided with open tops so that scrap metal of the desiredtypes and amounts can be loaded herein.

In order that the furnace 12 may be charged with scrap from the bins170, the latter are provided with removable bottoms whereby the contentsof a bin can be emptied when desired. Beneath the bins 170 above theplatform 166 there is provided a charging chute 176 having a roundedbottom. The charging chute 176 is disposed in a fixed position beneaththe bins 170 and each specific bin such as 170a, 170b, 170c and 170d maybe rotated to a position to discharge its contents through the bottomthereof into chute 176. he latter is dimensioned to receive the contentsof a single bin positioned above it and is positioned to discharge thosecontents toward the furnace 12. In order tocarry the scrap metal intothe furnace through the opening 70 normally closed by door 74, the chute176 is provided with a slidable extension chute 178. This extension,when extended, guide the material from the chute 176 directly into thefurnace, as shown in FIG. 10. Moreover, this extension 178 isretractable to the position shown in dotted lines in FIG. 11 so that thedischarge end of the extension chute clears the furnace structurewhereby the charging apparatus 100 can be moved along the rails 14without interference.

In operation, each of the bins 170a, 170b, 170c and 170d is loaded withthe proper types and amounts of scrap metal for a charge by any suitablemeans. The charging apparatus 160 is then positioned adjacent thefurnace l2 and the charging door 74 adjacent the receptacle 18 or 20 isopened. The chute extension 178 is then extended into the furnaceopening 70 and the bottom of the desired bin which has been rotated tobe positioned directly above the chute 176 is opened allowing the chargein the bin to pass through the chute 176 and extension 178 into thefurnace. The rate of charging is controlled by the amount the bottom ofthe bin is opened and as soon as the bin is empty, another bin is placedin position above the chute 176 for emptying. Thus, four different typesof scrap metal for charging the fumace can be carried in he system andcan be fed into the furnace by selectively rotating the bins 170 intoposition and opening the bottoms thereof to charge the furnace 12.

It will be understood that charging apparatus 160 requires considerablemore headroom than charging apparatus 13. It, too, however, may beprovided with means to raise the height of the charging chute inlet tocontrol the location of scrap deposit with respect to the area of thereceptacles 18 or 20.

While there have been shown and described several embodiments of thepresent invention, it will be understood that changes and modificationsare likely to occur to those skilled in the art and it is intended inthe appended claims to cover all those changes and modifications whichfall within the true spirit and scope of the present invention.

What is claimed as new and desired to be secured by Letters Patent ofthe United States is:

1. The method of converting an open-hearth furnace to a high-speedsteel-refining furnace which comprises, replacing the single shallowhearth of the open-hearth furnace with a pair of adjacent receptacleseach having a depth in excess of 4 feet, said pair of adjacentreceptacles taking up the same area as the single open hearth, providingmeans for individually charging each of said receptacles with moltenmetal, providing means for charging each of said receptacles with coldscrapiron, providing oxygen lance means selectively usable with eachreceptacle for blowing the charge of molten metal contained within thereceptacle with which said lance means is used, and providing means fordirecting thehot gases emitted from the receptacle with which saidoxygen lance means is used into intimate contact with the adjacentreceptacle for preheating material contained therein.

2. The method of claim 1 wherein the enclosure for the open hearth isreplaced by a pair of readily removable cover members one associatedwith each receptacle.

3. The method of claim 1 wherein the fuel supply means of theopen-hearth furnace is eliminated and the waste gas exhaust means isarranged so that waste gases may selectively be exhausted from eitherend of the said furnace.

4. The method of converting an open-hearth furnace to a high-speedsteel-refining furnace which comprises, replacing the single shallowhearth of the open-hearth furnace with a pair of adjacent receptacleseach having a depth in excess of 4 feet, said pair of adjacentreceptacles having approximately the same combined metal volume as thesingle open hearth, providing means for individually charging each ofsaid receptacles with molten metal, providing means for charging each ofsaid receptacles with cold scrap iron, the duct work connected to saidopen-hearth furnace being arranged so that waste gases may beselectively exhausted to the stack from either end hereof, providingoxygen lance means selectively usable with each receptacle for blowingthe charge of molten metal contained within the receptacle with whichsaid lance means is used, and providing means for directing the hotgases emitted from the receptacle with which said oxygen lance means isused into intimate contact with the adjusted receptacle for preheatingmaterial contained therein.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No3,632,489 Dated August 31 1971 Inventor(s) William A. Morton 8t 8.].

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Column 1, line 62, "taken" should read takes column 2, line 21,"molting" should read melting line 32, after "of", second occurrence,insert the line 45, "re" should read or column 4, line 2, after "become"insert more line 9, after "with", second occurrence, insert the line 48after "furnace" cancel of the furnace"; line 50, '10s" should read 16aand "10b" should read 16b line 61, "20" should read 26 line 70, "and",first occurrence, should read end line 71, cancel "are", secondoccurrence; column 5, line 4, after t" cancel "1''; line 8, "shallow"should read shallower --3 line 12, after "This" insert is line 30, after4 4b" insert and line 31, after "440" insert respectively. The ceilingwalls 42a and Mlc --5 line 43, after respectively. cancel "The covermembers 58 and 60 which are positioned adjacent each other to overliethe receptacles l8 and 20 respectively."; column 6, line 2 4, "flow"should read blow line 42, "99" should read 98 --5 line 43, "removable"should be removably line 47, after lace" cancel the comma and insert aperiod line 68 'those" should read these column 7, line 5 'in" shouldread is line 6, "19" should read l line 15, after "spout insert 90 line19, "68" should read 58 line 27, "one" should read on line 31, "72"should read 7 4 line 34, "Cases" should read Gases line 36, "those"should read these line 52, "n" should read an line 66, after "blowing"cancel the period and insert a comma same line "Allowing" should readallowing column line 10, "process" should read processes line 13,"process" should read processes line 42, "of" should read or k line 45,"and" should read made line 65, "he" should read the line 67, "king"should read kind line 75 PO-1050 (10-69) uscomwvoc GOZ-WB-F'OD 9 USGOVERNMENT PRINTING OFFICE 1 [BIB O--3l6-J34,

Patent NO. 3,602 ,4s9 Dated August 31, 1971 Inventor(s) A. MOItOn 2 Itis certified that error appears in the aboveidentified patent and thatsaid Letters Patent are hereby corrected as shown below:

"controlling" should read controlled same line, "FIG." should read FIGS.column 9, line 1, after "6", delete the end of parenthesis and insertand 7) line 3, "slidable" should be slidably lines 4-5, "retraction"should read retracted line 17, "the", first occurrence, should read insame line "the", third occurrence, should read in line 18, after- "136b"cancel "in order that scrap metal in the"; line 19, "136a" should read1360 line 29, "ad" should read and lines 31-32, "reception'fl-shouldread PBCGPtaOlEE same line, "10" should read l8 line 38, on maase"should read enmasse line 50, "of" should. I read or line 62, "12" shouldread 13 line 69, "130" should read 136 line 72, "130" should read 136line 74, after "the" cancel "charring apparatus 12 is movable the";column 10, line 21, "FIG" should read FIGS line 24, "100" should read160 lines 31-32, cancel "comprising apparatus 160 is provided with anundencarriage 161"; line 39, after "including" insert a same line,"1704:" should be 170a line 46, "herein" should read therein line 55,"he" should read The --5 line 57, "those" should read these line 6].,"guide" should read guides line 65, "100" should read 160 pomso (0435)USCOMM-DC come-peso i l) S GOVERNMENT PRONHNI. OPTIC! 19R 03b6-33'lUNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No. 3 602Dated August 3 97 William A. Morton PAGE 3 Inventor(s) It is certifiedthat error appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

column 11 line 6, "he" should read the column 9, line 62, 'id" ahouldread is Signed and sealed this 12th day of December 1972.

(SEAL) Attes'c:

EDWARD M.FLETCHER,JR. Attesting Officer ROBERT GOTTSCHALK Commissionerof Patents USCOMNPOC 00376-969 RM PO-105U (10-69] A u s covwuazur "mumsOFHCi 1 new o-usau,

1. The method of converting an open-hearth furnace to a highspeedsteel-refining furnace which comprises, replacing the single shallowhearth of the open-hearth furnace with a pair of adjacent receptacleseach having a depth in excess of 4 feet, said pair of adjacentreceptacles taking up the same area as the single open hearth, providingmeans for individually charging each of said receptacles with moltenmetal, providing means for charging each of said receptacles with coldscrap iron, providing oxygen lance means selectively usable with eachreceptacle for blowing the charge of molten metal contained within thereceptacle with which said lance means is used, and providing means fordirecting the hot gases emitted from the receptacle with which saidoxygen lance means is used into intimate contact with the adjacentreceptacle for preheating material contained therein.
 2. The method ofclaim 1 wherein the enclosure for the open hearth is replaced by a pairof readily removable cover members one associated with each receptacle.3. The method of claim 1 wherein the fuel supply means of theopen-hearth furnace is eliminated and the waste gas exhaust means isarranged so that waste gases may selectively be exhausted from eitherend of the said furnace.
 4. The method of converting an open-hearthfurnace to a high-speed steel-refining furnace which comprises,replacing the single shallow hearth of the open-hearth furnace with apair of adjacent receptacles each having a depth in excess of 4 feet,said pair of adjacent receptacles having approximately the same combinedmetal volume as the single open hearth, providing means for individuallycharging each of said receptacles with molten metal, providing means forcharging each of said receptacles with cold scrap iron, the duct workconnected to said open-hearth furnace being arranged so that waste gasesmay be selectively exhausted to the stack from either end hereof,providing oxygen lance means selectively usable with each receptacle forblowing the charge of molten metal contained within the receptacle withwhich said lance means is used, And providing means for directing thehot gases emitted from the receptacle with which said oxygen lance meansis used into intimate contact with the adjusted receptacle forpreheating material contained therein.